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  Multicomponent nanoparticles formed using a dispersing agentUSPTO Application #: 20060105910Title: Multicomponent nanoparticles formed using a dispersing agent Abstract: Nanoparticles include a plurality of two or more dissimilar components selected from the group of noble metals, base transition metals, alkali earth metals, and rare earth metals and/or different groups of the periodic table of elements. The two or more dissimilar components are dispersed using a dispersing agent such that the nanoparticles have a substantially uniform distribution of the two or more dissimilar components. The dispersing agents can be poly functional small organic molecules, polymers, or oligomers, or salts of these. The molecules of the dispersing agent bind to the particle atoms to overcome same-component attractions, thereby allowing dissimilar components to form heterogeneous nanoparticles. Dissimilar components such as iron and platinum can be complexed using the dispersing agent to form substantially uniform heterogeneous nanoparticles. The nanoparticles can be used alone or applied to a support. At least a portion of the dispersing agent can be removed by reduction and/or oxidation. (end of abstract) Agent: Workman Nydegger (f/k/a Workman Nydegger & Seeley) - Salt Lake City, UT, US Inventors: Bing Zhou, Sukesh Parasher, Michael Rueter USPTO Applicaton #: 20060105910 - Class: 502338000 (USPTO) Related Patent Categories: Catalyst, Solid Sorbent, Or Support Therefor: Product Or Process Of Making, Catalyst Or Precursor Therefor, Metal, Metal Oxide Or Metal Hydroxide, Of Group Viii (i.e., Iron Or Platinum Group), Of Iron The Patent Description & Claims data below is from USPTO Patent Application 20060105910. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application is a continuation-in-part of U.S. application Ser. No. 10/990,616, filed Nov. 17, 2004, the disclosures of which is incorporated herein in its entirety. BACKGROUND OF THE INVENTION [0002] 1. The Field of the Invention [0003] The invention is in the field of nanoparticles and/or catalysts that incorporate such nanoparticles. More particularly, the present invention relates to multi-component nanoparticles made using a dispersing agent that helps bring together and distribute different (e.g., dissimilar) components within the nanoparticles. [0004] 2. The Relevant Technology [0005] Nanoparticles are becoming increasingly more important in many industrial processes and products. Nanoparticles find use in a variety of applications, including catalysis and nanomaterials. Catalytic applications include uses for both supported and unsupported nanoparticles of various components, including precious metals, base metals, and oxides. Nanomaterial applications include uses for light blocking, pigmentation, UV absorption, antimicrobial activity, chemical mechanical polishing, and others. [0006] While useful nanoparticles may include only a single component (element or compound), it may be the case that advantageous properties can be achieved if the nanoparticles were to contain two or more distinct components to form a multicomponent nanoparticle. In general, combinations of two or more metals can have a variety of beneficial effects. In the case of catalysts, the use of different elements can modify the catalytic activity to improve an important performance parameter such as activity or selectivity, or they may make the catalyst particle or crystal more resistant to some deleterious effect, such as chemical poisoning or mechanical attrition. In the case of nanomaterials, the inclusion of two or more components would be expected to add additional functionality to the particles, such as combining light blocking function with UV absorption or anti-microbial activity. Alternatively, additional components might be expected to stabilize or strengthen the nanoparticles. [0007] While there is a strong motivation for producing multicomponent nanoparticles, it is difficult, if not impossible, to manufacture particles that contain two or more dissimilar components. This problem is particularly true of small nanoparticles. Recently, academia and industry have made significant advancements toward making very small particles. In some cases, the sizes of the particles are near or below 1 nanometer. [0008] While nanometer sized particles are very advantageous for producing desired properties such as increased catalytic activity and unique material properties, the very smallness of such particles makes it difficult, if not impossible, to create multicomponent nanoparticles that include dissimilar components or elements within the same nanoparticle. One reason for this difficulty is that similar or like elements or compounds have a greater affinity for each other than to dissimilar materials. This same-component attraction means each component has a propensity to combine and form particles with itself rather than forming a mixture with other, dissimilar components. As a result, multicomponent nanoparticle mixtures are largely heterogeneous, composed of two or more distinct particle compositions, each relatively rich in one component and largely depleted or devoid of the other dissimilar components. [0009] In general, the composition of particles, including the distribution of different components among and between the particles, is driven by thermodynamics. The chance of finding multiple components in any given particle depends to a large extent on the size of the particles being formed. Where the particles are relatively large, the probability is higher that two dissimilar components can be compounded within a single particle and/or form an alloy. As the size of the particles decreases, however, the likelihood of finding multiple components within a single particle decreases dramatically. At the nanometer scale, it is virtually impossible to consistently and predictably compound two or more dissimilar elements within a single nanoparticle using known procedures. Small nanoparticles tend to be all of one component or another. [0010] Part of the problem with forming multicomponent nano-sized particles is that conventional methods used to form nano-sized particles are performed at relatively low temperatures since high temperatures can causes nanoparticles to undesirably sinter or agglomerate together to form larger particles. Unfortunately, at such low temperatures, the thermodynamics of nanoparticle formation favors formation of single-component particles, as described above. On the other hand, raising the temperature sufficiently to overcome thermodynamic barriers to multicomponent formation causes agglomeration of smaller to larger particles. Consequently, conventional particle formation methods are not able to form nano-sized particles in which a substantial portion of the nanoparticles contain two or more components in each particle. [0011] Another factor that significantly affects the uniformity of multicomponent particles is the dissimilarity of the components. For example, two noble metals such as palladium and platinum are typically more easily combined together within particles because their electronic and chemical properties are similar. In contrast, a noble metal such as platinum and a base metal such as iron have different electronic and chemical properties and are thus much more difficult, if not impossible, to compound together in a single nanoparticle using conventional manufacturing methods. In many cases, compounding dissimilar components does not produce a viable nanoparticle system because of the lack of uniformity in the distribution of the components throughout the nanoparticles. This is particularly true in the case of catalyst particles that require both catalyst components to be in close proximity and/or to be alloyed together to generate the desired catalytic activity. [0012] R. W. J. Scott et al., JACS Communications, 125 (2003) 3708, state: " . . . at present there are no methods for preparing nearly monodisperse, bimetallic nanoparticles that are catalytically active . . . ." X. Zhang and K. Y. Chan, Chem. Mater., 15 (2003) 451, teach: "A number of techniques have been used for producing nanoparticles, including vapor phase techniques, sol-gel methods, sputtering, and coprecipitation. The synthesis of mixed metal nanoparticles is attracting a lot of recent interest for their catalytic properties . . . . The synthesis of mixed metal nanoparticles is a complex problem because of the composition control in addition to size and size distribution control. Platinum-ruthenium bimetallic catalysts have been prepared by co-impregnation methods but without good control of particle size, particle size distribution, and chemical composition." R. W. J. Scott et al., JACS Communications 127 (2005), 1380, disclose: "Most other methods for preparing supported bimetallic nanoparticles in the <5 nm size range lead to phase segregation of the two metals and thus poor control over the composition of individual particles." K. Hiroshima et al, Fuel Cells, 2 (2002) 31, teach: "The preparation of a highly dispersed alloy catalyst typically requires heat treatment, which is necessary to form an alloy but promotes particle aggregation. As a result, alloy catalysts usually have lower surface areas." [0013] Therefore, what are needed are multicomponent nanoparticles that include different components that are more evenly dispersed among the particles. Furthermore, what is needed are compositions and processes that can be used to bring together and compound different (e.g., dissimilar) components together in individual nanoparticles without destroying the nanometer size of the particles. BRIEF SUMMARY OF THE INVENTION [0014] The present invention relates to nanoparticle compositions that overcome the limitations of the prior art by providing "nano" sized particles that are composed of two or more components in a desired distribution. During manufacture, a dispersing agent binds the two or more components and maintains them in close proximity during nanoparticle formation in order to control the arrangement and/or distribution of the components in the nanoparticle material. [0015] In an exemplary embodiment, the multicomponent compositions of the present invention include a plurality of nanoparticles having a size less than about 100 nm. According to one embodiment, the plurality of nanoparticles includes at least two dissimilar nanoparticle components selected from different ones of the following groups: noble metals, base transition metals, alkali metals, alkaline earth metals, rare earth metals, and nonmetals. In an alternative embodiment, the multicomponent composition is made from two dissimilar nanoparticle components selected from two or more different groups of the periodic table of elements. The components that form the nanoparticles can be elements or compounds such as elemental metals or metal oxides. [0016] Preferably, at least about 50% of the nanoparticles include two or more dissimilar components. More preferably, at least about 75% of the nanoparticles include two or more dissimilar components, even more preferably at least about 85% of the nanoparticles include two or more dissimilar components, and most preferably at least about 95% of the nanoparticles include two or more dissimilar components. It is within the scope of the invention for at least about 99% (or essentially all) of the nanoparticles to include two or more dissimilar components. [0017] The present invention also includes a method to produce the uniform multicomponent nanoparticles. In general, the process includes preparing first and second solutions of dissimilar components and mixing them together with a dispersing agent to form a component complex. The molecules of the dispersing agent bind to at least a portion of the molecules of the first and second components to sufficiently overcome the same-component attractions such that the components can be arranged randomly or according to the molecular arrangement of the dispersing agent within the suspension. In some cases the component complex forms a suspension of nanoparticles. In other cases, the component complex is a precursor to the formation of nanoparticles (e.g., which may be formed by attaching the component complex to a support and/or removing at least a portion of the dispersing agent from the component complex). [0018] In one embodiment, a suspension of nanoparticles can be used as an active catalyst while remaining in suspension form. In another embodiment, the nanoparticles can be attached to or formed on a solid support by suitable impregnation or attachment methods. The nanoparticles can also be separated from some or all of the liquid to form a concentrate of nanoparticles or a dry powder. As needed, the suspension can be chemically modified to stabilize the nanoparticles (e.g., prevent agglomeration), adjust pH, or otherwise adjust composition to suit an end use application. In one embodiment, the nanoparticles can be isolated by removing the dispersing agent from the nanoparticles, such as under reducing conditions (e.g., by reducing under H.sub.2 gas or using strong reducing catalysts such as lithium aluminum hydride, sodium hydride, sodium borohydride, sodium bisulfite, sodium thiosulfate, hydroquinone, methanol, aldehydes, and the like, or by oxidation such as by using molecular oxygen, hydrogen peroxide, organic peroxides, and the like). [0019] In an exemplary embodiment, the nanoparticles of the present invention are also of a substantially uniform size such that the particle size distribution (or deviation) is extremely narrow. The substantially uniform particle size distribution produces a nanoparticle material with more consistent properties and activity throughout the material. [0020] The nanoparticles and methods of the present invention provide many advantages for making novel nanomaterials such as catalysts and/or for improving the activity and performance of existing nanomaterials. Novel nanomaterials are possible because dissimilar components, which typically do not form uniform particles, can be combined using one or more dispersing agents such that most or all of the particles have the two or more components in each particle. Because each nanoparticle contains a mixture or alloy of the two or more components, each nanoparticle has the intended or desired characteristic needed to produce the properties of the multicomponent material. [0021] Unlike the nanoparticles of the prior art, the dissimilar components in the nanoparticles of the present invention are evenly dispersed among the nanoparticles. The dispersing agent overcomes the tendency for like components to agglomerate and form homogeneous particles but instead helps form multicomponent particles. In many cases, the functionality of the material depends on forming heterogeneous (i.e. multicomponent) particles rather than forming a heterogeneous mixture of homogeneous (i.e., single component) particles, as is typically seen in the prior art. The proper dispersing and mixing of the two or more components according to the present invention imparts beneficial characteristics, such as those described above. [0022] Another advantage of the present invention is that the dispersing agents are readily available and relatively inexpensive. Still another advantage of the inventive process is that it is highly flexible in that it works well with a variety of components and thus can be used to improve many new and existing catalysts and nanomaterials. Furthermore, existing and novel catalysts can be stabilized thereby providing opportunities to use the nanoparticles in new processes or improve the resistance of the nanoparticles to degradation. Continue reading... Full patent description for Multicomponent nanoparticles formed using a dispersing agent Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Multicomponent nanoparticles formed using a dispersing agent patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. 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